I took my 40d to the duck blind this past weekend with very poor results. It was really struggling with autofocus with the lens searching, searching and not usually finding. I have read many of the old posts on the topic. Many suggest user error while others suggest the need to send the camera to Canon. Some posts suggest resetting the camera to factory settings. I have the camera set on center point focus using the * button. I can understand the difficulty in getting hand held focus on an individual bird in flight, so I took different sets of photos. Some with ducks in water, some in flight both single shot and multiple shot. My hope was that if my first shot was off, that the autofocus feature would take over and correct the focus. Maybe I don't understand autofocus but it did seem to happen. The final two shots are of the decoys sitting in water. The focal point is the two grey duck decoys. The first photo was with the focusing button and the second using live feature. The second easily out paces the first.

Bottom line, I only use the 40D as a backup to my 7D. If it is a focus issue with me, then I'll just have to keep practicing. If it is a camera issue, then I'll have to decide whether to sell it (with full disclosure of my concern) or send it to canon. I am debating the former replacing it with a less expensive T3i. Before I take action, I wanted your thoughts. Thanks.

Ok as a long time 40D user I find that it's AF is good as long as the thing your aiming at is either not moving or not small and if if the target is small and moves then pretty much forget it.
It is also slightly lens dependant but also it's servo setting is pretty much pointless at full fps.

Example I was shooting a running dog(towards me) and at 6.5fps the hit rate was almost none (dog is pretty quick) but at the 3.5 fps the hit rate was better . So I'll take less frames but some in focus than loads of OOF ones.
I have managed some fairly good moving stuff like birds but it's more luck than a good AF servo.
It wasn't until I used a 1 series (with the same lenses) that I realised how bad the 40d was .

My 40D is still loved and is used as a general cam usually with the AF set to single shot (I find ai does a good enough job also) and I leave any thing servo to my 1D2n

Camerajunqie wrote:
I took my 40d to the duck blind this past weekend with very poor results. It was really struggling with autofocus with the lens searching, searching and not usually finding. ...I have the camera set on center point focus using the * button. ...The final two shots are of the decoys sitting in water. The focal point is the two grey duck decoys. The first photo was with the focusing button and the second using live feature. The second easily out paces the first.

Live View Focus is often more accurate than standard focus due to its use of contrast detection rather than phase detection, but it's slower so not always practical.

In your case, I think the relatively dim lenses, coupled with the "shades of gray" ducks against the shades of gray water and sky, made autofocus a difficult propostion.

That said, if I look at the targets your camera would have locked onto (red arrows) it didn't actually do too badly. As mentioned above, a higher ISO setting would have allowed a faster shutter (1/1000 or more helps to freeze beating wings), which may have helped improve sharpness.

Also, there may be a little back-focusing issue. The first decoy shot seems to have focused on the duck (green arrow) behind the target duck (red arrow). The Live View Focus shot (last of my examinations) seems to have locked onto the ducks you intended it to.

Thanks for the input. I worked with the camera's settings yesterday comparing it to exact same shots from 7D. Clearly the 7d smokes the 40d. The 40d improved with adjustments but I can't see it being a back up in situations where I don't want to bring my 7d. Don't have funds to move up, so I still lean toward the T3i which I believe has the Canon's newest AF. What do you think?

BTW, if you are near Creole, Louisiana, there is a WL Refuge on Highway 27. The refuge has a 3 mile circle called Pintail Drive. It is between duck splits. The back portion is loaded with birds. Caveat, you're ability to get out of the car on the circle is prohibited and at best very limited so bring a driver.

So many negative comments about 40D AF. I wish I had some of that as moral support when I first complained about mine a few years back. Instead I got bagged for daring to mention its incompetence.

Doug, were you using IS for the 100-400 shots? If not then you have a problem with inadequate shutter speed. You probably need 1/FL/1.6 or faster even for static subjects.

If you were using IS then did you give it time (one second) to settle before shooting ?

Did you also aim the lens correctly *before* activating the AF ? Otherwise it can try to track the wrong thing or nothing.

Keep in mind that although a faster ISO increases noise and decreases dynamic range, the increase in shutter speed can make the subjects much sharper. You can apply noise reduction later on but de-blurring is much closer to impossible. If in doubt then opt for more shutter speed. No need to go over the top but don't leave it at or near bare minimum when you don't really need to.

I'm surprised the 40D focused at all with an f/8 lens/TC combination - unless the focal length was short enough for the lens to have a brighter maximum aperture than the f/5.6 which applies at most longer FLs.

In AI Servo the camera might have happily fired away without actually ever confirming focus. Did it indicate focus or were you too distracted looking at the subjects to see the focus indicator ? It happens. To amateurs. Or so I'm told Actually it is all too easy to let it happen.

Did the lens have a UV or similar filter on it ? If so then try again without the filter. Sometimes a filter can make a big difference to image sharpness.

I am not familiar with the T3i but having the newest AF need not make it better or even good. At one stage the 40D was the newest but mine never worked well.

Camerajunqie wrote:
Thanks for the input. I worked with the camera's settings yesterday comparing it to exact same shots from 7D. Clearly the 7d smokes the 40d. The 40d improved with adjustments but I can't see it being a back up in situations where I don't want to bring my 7d. Don't have funds to move up, so I still lean toward the T3i which I believe has the Canon's newest AF. What do you think?
.

Ok 2 points.

1 if I had both the 40d and 7d , I could think of no situation where I would rather bring the 40D over the 7D . The difference in dimensions and weight are so minimal as to be nothing .

2 the rebel range have an AF system that's lower grade than the XxD system . Now they may have tweaked the firmware but I would not say it would be a definite upgrade. Im not going to dis the 40D's system too much as most of the time mine is pretty dam spot on. On mine it's just when the target moves it struggles more than my 1series ( no surprise there)
I did try a 50D for a while which has much the same system but with the added advantage of MA. It did very slightly better but nothing worth keeping the 50D.

For a full rundown on the different AF systems have a look at the digital picture web site . It gives a fair bit of info.

I would first mount the 40D on a tripod and test the AF on a stationary subject with the lens you plan to use. If its not focused sharply, going any further is a waste of time until you get it adjusted.

If its accurate, rember that the object you are focusing on needs to be fairly large in the viewfinder. The 40D is not really capable of picking out one bird in a flock to focus on, it may very well pickup the closest one. I've had five 40D's and loved everyone of them, but my 7D and 1D MK III are so much better at focus of small moving things.

Like Brian said, you seem to have back focus problem on at least two images.

Plus, the image of the two ducks on water has camera movement blur.

The others seem to have missed focus, possibly due to low contrast or subject movement too fast for AF system. Also, effective f/8 on your lens+ext may be too dark for the AF.

Try to borrow an older 1D2 or 1D3 and see that improves things for you. And shoot from a tripod or monopod. Use a fast shutter speed -- for flying birds, go for 1/800 or higher. You might also confirm at home whether you have back focus. Then decide to repair or sell and buy a better back-up, like the 1D2 or even the T3i or 60D.

Alan, the answers to your questions are yes, yes, yes, guilty of not looking and no filter.

Ian & Scaleusa, there was no way that I was bringing my 7d to the blind on this hunting trip. Had gun, shell bag, camera and way to much salt in the water for me to risk. On another, non-hunting trip, I will bring the 7d but I will be able to secure it with my full attention.

Alan321 wrote:
...Doug, were you using IS for the 100-400 shots? If not then you have a problem with inadequate shutter speed.

For fast-moving subjects, IS isn't always enough. His BGs look reasonably steady, but the duck's head in the retriever shot, for example, is blurred while the dog isn't, and it was shot at 1/60. In the new group of images, the one of the duck making a water landing is sharp, and it was shot at 1/1600. The need for a faster SS is, I think, indicated in some of the shots.

Alan321 wrote:
...Did you also aim the lens correctly *before* activating the AF ? Otherwise it can try to track the wrong thing or nothing.

I think that was a big part of the problem. In the sample images, the ones that were in focus had a subject (or part of a subject in the case of large objects like dogs and people) right in the center of the frame, and in the ones that were OOF the subjects weren't centered.

Camerajunqie wrote:
BTW, not all shots came out bad but the keep ratio was very low.

The biggest problem in the flock-in-flight shots may be insufficient depth of field, in addition to missed focus target. With long lenses, f/8 gives a DoF that may not be deep enough to get all the ducks in the flock equally sharp.

Moving from 200 ISO to 400 or 800 could help all the noted problems except aim-point.